Electron-discharge device and circuit therefor



Apriii m 1928. 9,665,508

5. E. SCHUMACHER ELECTRONDISCHARGE DEVICE AND CIRCUIT THEREFOR FiledOct. 22, .1924

Patented Apr. 10, 1928.

UNITED STATES 1,665,508 PATENT OFFICE.

EARLE E. SGHUMACHER, OF EAST ORANGE, NEW JERSEY, ASSIGNOR 'I'O WESTERNELECTRIC COMPANY, INCORPORATED, OFNETW' YORK, N. Y., A CORPORATION OFNEW YORK.

ELECTRON-DISCHARGE DEVICE AND CIRCUIT THEREFOR.

Applicatiomfiled October 22, 1924. Serial No. 745,085.

charge has been established between the.

cathode and anode of the device, the cathode heating means may bediscontinued without material diminution of the space current, provideda sufiiciently high potential is maintained between the cathode andanode. This arrangement eliminates one source of power withoutpreventing the continued.

emission from the coated cathode to the anode.

Referring to the drawings:

Fig. 1 shows diagrammatically a circuit for carrying this invention intoeffect.

Fig. 2 is a V-shaped filament for an electron discharge device with aportion broken away to show the relative thickness of the core and theactive coating.

In carrying this invention into effect, a highly refractory filamentcore 10, such as tungsten, molybdenum or the like, is heated to a hightemperature, in vacuum, and finely powdered, thermionically activematerial brought in contact with the refractory core, to provide a thickand shaggy coating 11, having high electron emissivity.

A cathode of this character may be obtained by supporting a refractorycore 10 .in a glass vessel 12 containing a grid 13' and a plateelectrode 14. A quantity of powdered material of high thermionicactivity, such as barium and strontium oxides is placed in the vesseland the vessel highly evacuated and sealed ofi in the usual manner. Apower source of sufiicient voltage, is connected to the filament leadsand the filament core heated to a suitable-temperature, which in thecase of barium and strontium oxides is between 700 and -1000 C. Thevessel is then shaken to bring the thermionically ac material have beentaken up by the cathode, to provide a relatively thick coating. Thethickness of the coating obtained in this way depends upon thetemperature of the filament core, and also upon the degree of vacuumobtained in the device, which may be a proximately of a pressure of 11O- mm.

g. or less. After the desired thickness of coating has been obtained,the ti of the glass vessel maybe broken and t e excess material removedand the vessel again evacuated and sealed. Due to this method ofcoating, the thermionically active material adheres to'the incandescentcore of the filament and forms a thick, shaggy coatin having a surfacewhich is composed 0 minute points or edges, giving the filament coatinga rough appearance. This method is described and claimed in my copendingapplication, Serial No. 650,985, filed July 12, 1923 entitled Electronemitting cathodes and method for making them.

However, other methods may be used which will produce a thick and highlylaciniated coating on the refractory filament core. The coating obtainedin this manner has'good. thermionicproperties and does not deterioratereadily.

A plurality of leads 15, are attached to the electrodes within thevessel and are sealed within the press 16 of the vessel 12. The filamentor cathode 10 is connected to a battery 17, through conductors 18 and19, and a switch 20, by means of which the battery 17 may bedisconnected from the filament 10. The control electrode 13 is comnected to the cathode by conductor 21, the secondary winding of theinput transformer 22, and battery .23 which maintains the controlelectrode negative with respect'to the filament. The plate electrode 14is connected to the cathode by conductor 24 through the primary windingof the output transformer 25, and battery 26 which impresses adifference of potential between the cathode and anode.

The method of bperation consists of closing the switch 20, whereuponheating current is supplied to the filament. Simultaneously, a spacedischarge is established between the cathode and the anode by thebattery 26, which maybe between 250 and 500 volts, or sufficient to heatthe anode to a red glow. The switch 20 may be opened immediately withoutdiscontinuing the operation of the device, and the electron emissionfrom the filament will. continue as long as the voltage of the platebattery is sufliciently high. The dissipation of energy in the coatingby the flow of space current ther'ethrough maintains it sufficiently hotto cause the emission of electrons.

By this arrangement, an electron discharge device containing a cathodehaving a thick and shaggy coating may be utilized in'a variety ofcircuits such as, detectors, amplifiers, oscillators and repeatercircuits, and maintain continuous electron emission from the cathodeover a considerably long period of time without being supplied with acontinuous heating current from a separate battery.

Although the invention has been described with reference to a particulararrangement, it is, of course, understood that various modifications maybe made in the construction and method of operation without departingfrom the scope of the invention as covered in the appended claims.

What is claimed is:

1. In combination an electron discharge device having a cathode and ananode, an

output circuit comprising said cathode, anode and a source of current,and a source of heating current for said cathode, said cathodecomprising a. metal core having a thick shaggy thcrmionically activecoating, means for closing said heating circuit to establish the spacecurrent flow between said cathode. and anode, and for thereafteropeningsa-id heating circuit, the dissi ation of energy in the coatingby the flow 0 space current therethrough maintaining the samesufficiently hot to cause it to emit electrons.

2. In combination an electron dischar e device comprising a cathode andan anor e, an output circuit therefor containing a source of current, asource of heating current for said cathode, and means for disconnectingsaid cathode source, said cathode comprising a filament having a thickshag y coating, the dissipation of energy in t e coating by the flow ofspace current therethrough maintaining the same sufiiciently hot tocause it to emit electrons.

In witness whereof, I hereunto subscribe my name this 18th day ofOctober, A. D. 1924.

EARLE E. SCHUMACHER.

